/Engine/Source/Runtime/Engine/Public/ParticleHelper.h
void CalculateParticleTransform ( const FMatrix & ProxyLocalToWorld, const FVector & ParticleLocation, float ParticleRotation, const FVector3f & ParticleVelocity, const FVector3f & ParticleSize, const FVector3f & ParticlePayloadInitialOrientation, const FVector3f & ParticlePayloadRotation, const FVector & ParticlePayloadCameraOffset, const FVector3f & ParticlePayloadOrbitOffset, const FVector & ViewOrigin, const FVector3f & ViewDirection, FMatrix & OutTransformMat ) const